SCISAT, a Canadian satellite launched in 2003, measures the concentrations of more than 30 different molecules in the stratosphere, by monitoring what wavelengths of light they absorb at sunrise and sunset. Its primary mission is to monitor the ozone layer and learn more about which chemicals affect ozone, to help formulate international environmental policy. It also measures molecules related to biomass burning and industrial activity, and greenhouse gases. SCISAT is one of many satellites around the world monitoring the composition of the atmosphere and helping to understand how human activity affects it.
Satellites also assist environmental monitoring on the surface of planet. When oil is spilled in the ocean, it’s essential to quickly determine where the spill is, how big it is, which direction it’s moving in, and what wind and wave patterns will affect it. Satellites equipped with a laser fluorosensor can detect oil on land, water and ice, and can even determine what kind of oil it is. Forest fires are also monitored by satellite: thermal infrared sensors can detect active fires and dormant hot-spots, even when the view is obscured by smoke and haze.